The invention relates to conditionally-stable high order multi-path operational amplifiers.
An operational amplifier is a relatively high gain amplifier capable of being used in various kinds of feedback circuits. An operational amplifier circuits can, for example, provide programmable gain, signal summation, integration, and differentiation, and various other useful functions.
The most popular variety of operational amplifier has high-impedance differential signal inputs and a low impedance signal output, and functions as a high-gain differential voltage amplifier. Another kind of operational amplifier, known as an xe2x80x9coperational transconductance amplifier,xe2x80x9d has high-impedance differential signal inputs and a high-impedance signal output, and functions as a differential voltage to current converter.
An amplifier is disclosed including multiple integrator stages. The multiple-stage amplifier includes an attenuator/low-pass filter, which serves to condition the signal passing through the amplifier. This attenuator/low pass filter is in the low frequency or DC path, it can cause the offset in the second stage integrator to be multiplied by the attenuation factor of the attenuator or low-pass filter, when referred to the output of the first-stage integrator. This multiplied offset, when input referred, can be a dominant contributor to the overall offset of the amplifier.
Disclosed in this application is the placement of an additional integrator between the first stage integrator output and the input to the attenuator/low pass filter. This approach reduces the input referred offset of the second stage integrator by a factor equal to the gain of the additional integrator, and the offset of the additional integrator itself will be divided by the gain of the first-stage integrator.